The purpose of this study is to evaluate the pharmacokinetics (PK) of ustekinumab in subjects from 2 through less than (<) 18 years old in the USA, or 6 through less than (<) 18 years old in other countries and determine if it is similar to that observed in adults with moderately to severely active Crohn's disease (CD). Also to assess the safety, immunogenicity and efficacy of ustekinumab in the treatment of moderately to severely active CD. The main part of the study continues to Week 16, at which point all subjects who are receiving benefit from ustekinumab maintenance therapy (as determined by the investigator) are eligible to enter the long-term extension (LTE) and continue to receive ustekinumab. The study extension ends at Week 236.

Clinical Response is defined as greater than or equal to (>=) 15-point reduction from baseline in the total Pediatric Crohn's Disease Activity Index (PCDAI) score, accompanied by a total PDCAI score of less than or equal to (<=) 30 points. PCDAI is an index used to measure disease activity of pediatric patients with Crohn's Disease assessing abdominal pain, stool frequency, patient functioning, hematocrit, erythrocyte sedimentation rate, albumin, weight, height, abdominal tenderness or mass, perirectal disease, and extraintestinal manifestations. It ranges from 0 to 100; higher scores indicate more active disease.

Subjects will receive a single intravenous (IV) induction dose of 3 milligram per kilogram (mg/kg) for subjects less than < 40 kilogram (kg) or 130 milligram (mg) for subjects greater than or equal to >= 40 kg at Week 0 followed by subcutaneous (SC) maintenance dose of 2 mg/kg for subjects < 40 kg or 90 mg for subjects >= 40 kg at week 8.

Drug: Ustekinumab

Subjects will receive a single IV administration of ustekinumab (3 mg/kg for subjects <40 kg or 130 mg for subjects >= 40 kg in Group 1 and 9 mg/kg for subjects < 40 kg or 390 mg for subjects >= 40 kg in group 2) at week 0 followed by SC administration of ustekinumab (2 mg/kg for subjects < 40 kg or 90 mg for subjects >= 40 kg at Week 8.

Experimental: Group2: Ustekinumab Dose Regimen 2

Subjects will receive a single Intravenous (IV) dose of 9 mg/kg for subjects <40 kg or 390 mg for subjects >= 40 kg at Week 0 followed by SC maintenance dose of 2 mg/kg for subjects <40 kg or 90 mg for subjects >= 40 kg at week 8.

Drug: Ustekinumab

Subjects will receive a single IV administration of ustekinumab (3 mg/kg for subjects <40 kg or 130 mg for subjects >= 40 kg in Group 1 and 9 mg/kg for subjects < 40 kg or 390 mg for subjects >= 40 kg in group 2) at week 0 followed by SC administration of ustekinumab (2 mg/kg for subjects < 40 kg or 90 mg for subjects >= 40 kg at Week 8.

Eligibility

Ages Eligible for Study:

2 Years to 17 Years (Child)

Sexes Eligible for Study:

All

Accepts Healthy Volunteers:

No

Criteria

Inclusion Criteria:

Be a pediatric subject 2 to less than (<) 18 years old in the US, 6 to <18 years old elsewhere, of either gender with a body weight of greater than or equal to (>=) 10 kilogram (kg)

Have Crohn's disease (CD) or fistulizing CD of at least 3 months duration, with active colitis, ileitis, or ileocolitis, confirmed at any time in the past by radiography, histology, and/or endoscopy

Must have moderately to severely active CD defined by: Baseline pediatric Crohn's disease activity index (PCDAI) score of greater than (>)30 and at least one of the following: An abnormal C-reactive protein (CRP) >0.3 milligram per deciliter (mg/dL) or 3.0 milligram per liter (mg/L) at screening) or fecal calprotectin >250 milligram per kilogram (mg/kg) at screening or ileocolonoscopy with evidence of active CD (defined as ulcerations in the ileum and/or colon) during screening into this study including at the baseline visit

Prior or current medication for CD must include at least 1 of the following: Current treatment with at least 1 of the following therapies: oral corticosteroids, the immunomodulators azathioprine, 6-MP, or methotrexate, or currently have or have had a history of corticosteroid dependency, or have a history of failure to respond to, or tolerate, at least 1 of the following therapies including oral or IV corticosteroids or the immunomodulators 6-mercaptopurine, azathioprine, or methotrexate,or have required more than 3 courses of oral or IV corticosteroids in the past year

Have negative stool results for enteric pathogens. Stool studies must include a stool culture and Clostridium difficile toxin assay. These must have been performed during screening or the current episode of disease exacerbation as long as the stool studies were performed within 4 months prior to the first administration of study agent

Exclusion Criteria:

Has complications of CD such as symptomatic strictures or stenosis, short gut syndrome, or any other manifestation that might be anticipated to require surgery, could preclude the use of the PCDAI to assess response to therapy, or would possibly confound the ability to assess the effect of treatment with ustekinumab

Currently has or is suspected to have an abscess. Recent cutaneous and perianal abscesses are not exclusionary if drained and adequately treated at least 3 weeks prior to baseline, or 8 weeks prior to baseline for intra-abdominal abscesses, provided that there is no anticipated need for any further surgery. Participant with active fistulas may be included if there is no anticipation of a need for surgery and there are currently no abscesses identified

Has had any kind of bowel resection within 6 months or any other intra-abdominal surgery within 3 months prior to baseline

Has a draining (that is (i.e.), functioning) stoma or ostomy

Presence or history of any malignancy including presence or history of lymphoproliferative disease including lymphoma, or signs and symptoms suggestive of possible lymphoproliferative disease, such as lymphadenopathy of unusual size or location (example, nodes in the posterior triangle of the neck, infraclavicular, epitrochlear, or periaortic areas), or clinically significant hepatomegaly or splenomegaly

Contacts and Locations

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To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below.
For general information, see Learn About Clinical Studies.

Please refer to this study by its ClinicalTrials.gov identifier: NCT02968108